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[untune]

I've got all the stuff I need to build a couple of tape delay units, just finalising the design.. I've been pondering the use of multiple playback heads.  So just a quick question for anyone who might know - can you just solder additional mono playback heads to the same points on the board as the original one, or does there need to be additional circuitry?

Cheers

[moordenaar]

Could be. If not you need to make some preamps.

[Circuitbenders]

You're probably going to at least need some kind of mixer circuit, that way you can control the level of each head as well.

[untune]

Cheers for the input.  If it's going to be a lot of additional work it's probably not worth bothering - I was simply going to have 3 or so, complete with switches to add/remove them from the mix.  Though a passive mixer circuit would be relatively simple, not hard to build that seperately and insert it between heads/board.

I always thought tape players had very specific preamp circuits to handle the bias/EQ etc?

Also on the subject, these tape machines are identical but only have a headphone output and a microphone input, both minijacks.  Can these be modified to be line in/line out, without much hassle?  I know I've seen this elsewhere on the forum, but thought I'd ask specifically for this application.  Could also disconnect the internal speakers and use them as line outs instead?

Cheers

[Gordonjcp]

You only need to worry about bias on record.  Playback just needs a preamp with a bit of treble roll-off, for non-hifi use ;-)

[untune]

You only need to worry about bias on record.  Playback just needs a preamp with a bit of treble roll-off, for non-hifi use ;-)

Thanks Gordon!  I thought that was the case.  That's reminded me I've got a nice reel to reel here that has something wrong with the bias oscillator, but I've no idea how  to reapir it :S  That's a project for another day though

That should be fine then.  Tape recorders I'm using only have a range of 150-8000Hz so hardly hi-fi to begin with

[untune]

This is more of an electronics question - if I have 2 identical recorders that run off 3v adapters, how can I power them both from 1 plug?

This is one thing I somwtimes wonder about, but have never found the answer for.  I see a lot of schematics for different audio circuits ranging from 5v to 15v input.  How do you cater for different voltages and only have one power source?  Haha that sounds so daft when I type it, can't think of any other way to put it

Lets say for example you had a keyboard that ran at 6v and you had a schematic for a filter circuit that used 12v.  What's the solution for interfacing the two?  Is it even possible?

[Circuitbenders]

use a 12v voltage regulator for the 12v, and then run the output of that into into a 6v regulator for the 6v. You'll need to supply about 15v or so to the input of the 12v regulator.

Or am i misunderstanding the question?

Theres no reason why you can't run as many circuits as you want from the same power supply, as long as it can deliver enough milliamps.

[untune]

That's made it clearer, thanks

So in the case of running 2 tape recorders from the same 3v adapter - what would I need to wire up?  I dug around in my components drawer and found an unopened box of 10x LM317T voltage regulators.  Think I bought them ages ago to do a tape motor speed mod but never got round to using them.  They of any use here?

[Circuitbenders]

Just wire the power inputs to both of them to the same power socket, you don't need anything else if they both run from the same 3v power supply. As long as the power supply you use can deliver enough milliamps to run them both, which is most probably can, then its not any more complicated than that.

[untune]

Ace, I always thought it'd be more complex than that   Cheers!

Recorders arrived today, not had time to test them properly yet but they're fairly dirty.  Also a bit of a 'blast' of hiss when you press play that quickly fades off.  Got some snooping to do!

[untune]

On a relaetd subject, I have a couple of old rim drive 'spycorders' - ie the old mini reel to reels from the 60's.  Bit awkward as each one has 3 batteries - a 9volt, and a pair of what I think are C cells (=3v?).  If I remember right, one supply drives the motor and the other the electronics.  There's no power jack for these units, which is really inconvenient.  Is there any way I can hook both these units up so that I could power them with a single plug?  I was hoping to make a reel to reel style delay out of these eventually and it'd be a bit of a hassle having 6 seperate batteries to run the whole thing

One of them has had the 9v supply snipped at some point so I was going to have to re-wire one of them anyways

[untune]

Sorry if this appears ignorant, I've only just clocked that pretty much the same discussion is going on in another thread

[Circuitbenders]

If i have some spare time anytime soon i'll put together a basic tutorial on powering stuff with some links and put it in the Bending Tips section.

[jamiewoody]

you may have different  options in ragard to a mechanical delay like this. i may be wrong, just brainstorming...

how about multiple record heads?
instead of multiple play heads, make one play head movable.
instead of one movable play head, make multiple movable play heads.
how about single or multiple movable recording heads?
a pitch (speed) control
a microphone input, so you can talk, sing, scream through it!
2 inputs and 2 outputs...do a loop between input and output....might be cool!
build two tape delays into one box...maybe you could do realtime COMB FILTERING! ;-)
build a tube and a breathalizer, to see if you are sober enough to drive home ;-)